The disclosed embodiments relate to methods and systems for printing print jobs and, more specifically but not exclusively, to methods and systems for printing jobs in electronic imaging printing systems in a manner that reduces delays in processing print jobs.
The terminology “imaging” refers to the entire process of putting an image (digital or analog source) onto paper.
Imaging printing systems utilize a raster image processor (RIP) that provides output data in a format that is suitable for printing by a printer. One suitable format is raw, binary dot patterns forming a bitmap. The raster image processor receives input of one or more page descriptions. The page descriptions include information about fonts, graphics, and the like that describe the appearance of each page. The page descriptions may be in a high level language or even another bitmap of higher or lower resolution than the output device. Some examples of high level page description languages are PostScript (PS), Portable Document Format (PDF) and Extensible Markup Language (XML) Paper Specification (XPS). The raster image processor may be implemented either as software, firmware, or hardware. Typically, the raster image processor resides in a digital front end (DFE). The raster image processor performs raster image processing (ripping). Raster image processing is the process of translating the page descriptions into a bitmap for output by the output device.
Imaging printing systems also generally provide for permanently fixing an image to a substrate, typically paper, by fusing, drying, or other means. The printing systems can include pre-cut sheet printing machines or continuous web feed printing machines. Printing systems that utilize pre-cut sheet machines are configured to print onto cut sheet substrates and typically include copy sheet paper paths through which copy sheets (e.g., plain paper), which are to receive an image, are conveyed and imaged. The process of inserting copy sheets into the copy sheet paper path and controlling the movement of the copy sheets through the paper path to receive an image on one or both sides is referred to as “scheduling”. Copy sheets are printed by being passed through a copy sheet paper path (which includes a marking station) one or multiple times. Copy sheets which are printed on only one side (simplex copy sheets) in a single color usually pass through the copy sheet paper path a single time. Multipass printing is used to print images on both sides of a copy sheet (duplex printing), or to print a simplex sheet in multiple colors (one pass for each color).
On-line finishing devices can also be integrated with imaging systems. These on-line finishing devices directly receive copy sheets as they are outputted from the imaging system and perform various types of finishing operations on each copy sheet, or on each set of copy sheets. The finishing operations can be, for example: binding, stitching, folding, trimming, aligning, rotating, punching, drilling, slitting, perforating, and combinations thereof.
High speed printing of document images by xerographic, ionographic, ink jet or other copiers, printers, or other reproduction apparatus (encompassed by the word printers here) has become increasingly important and increasingly demanding in terms of quality, reliability, and other features.
For very high speed or high volume copying or printing, it is desirable to use a printing system that employs a continuous web print substrate. In web feeding, instead of feeding pre-cut sheets to be printed, the image substrate material is typically fed from large, heavy rolls of paper, which can be from paper mill rolls, and thus provided at a lower cost per printed page than pre-cut sheets. Each such roll provides a very large (very long) supply of paper printing substrate in a defined width. (Fan-fold or computer form web substrate can also be used in some limited printing applications, e.g. where edge sprocket hole feeding is desired.) Typically, with web roll feeding, the web is fed off the roll and through the xerographic or other print engine to be printed and thereafter cut in a chopper and/or slitter at or after the printer output to form the desired copy sheets. Alternatively, the printed web output can be rewound onto an output roll (uncut) for further processing off line.
Web paper has feeding and printing reliability and plural image registration advantages as compared to conventional precut sheets. That is, in addition to the cost advantages, web feeding can also have advantages in feeding reliability, i.e., lower misfeed and jam rates within the printer as compared to high speed feeding of precut sheets through a printing apparatus. A further advantage is that web feeding from large rolls requires less downtime for paper loading. For example, it is not uncommon for a system printing onto web paper from a 5 foot diameter supply roll to print continuously for an entire shift without requiring any operator action, compared to the need for an operator to re-load cut sheet feeders 2 to 3 times per hour on a typical cut sheet feeder system of equivalent speed. Continuous web printing also provides greater productivity for the same printer processing speed and corresponding paper path velocity through the printer since with web printing the images can be printed in direct sequence with no pitch space skips between images as is required between each sheet for cut sheet printing.
Web feeding is more suitable where the same substrate can be used for all or most of long runs of single sheet documents, or multi-page multiple print jobs in a printing run, all to be printed on the same substrate media. Quickly or easily changing between substrates is much more difficult with a web fed machine than a cut sheet machine. In a cut sheet machine, different sheets of different sizes, weights, colors, pre-prints, holes, etc. can be loaded into different paper feeding drawers and easily changed or substituted.
In view of ever increasing demand for efficient print production, it is desirable to minimize substrate wastage and avoid stoppages or shutdowns wherever possible. For very high speed continuous feed presses, even an orderly quick shutdown can waste dozens of feet of web media and may require a pre-print setup before paid content can be printed again.
There is a general need for printing systems and methods that can provide more efficient print production. It is believed that the methods and systems of the illustrative embodiments help meet this need.